The invention concerns a process for the manufacture of short circuits on the anode side of thyristors which have an anode base zone of the first conducting type and an emitting zone on the anode side of the second conducting type.
Short circuits on the anode side are essential for GTO thyristors, because no short circuits are possible on the cathode side in this case. They are also advantageously employed, in addition to short circuits on the cathode side, in asymmetric thyristors--that is, those thyristors that only block in the discharge direction, since by this means the storage load on the anode side of the semiconductor body--and consequently the recovery time can be reduced.
The purpose of the invention is to describe a particularly simple process for the manufacture of this kind of short circuit on the anode side. In particular, this process requires only a single additional mask. This purpose is accomplished by the following steps:
a) a zone of the second conducting type is generated over the entire surface on the anode side in the semiconductor body of the first conducting type, PA1 b) the entire surface of this zone is covered with a masking layer, PA1 c) the masking layer is structured by photolithography, PA1 d) grooves are etched in the semiconductor body according to its structure which extend through the zone of the second conducting type as far as the anode base zone, PA1 e) in the grooves, zones of the first conducting type are generated, which have a higher doping concentration that the anode base zone, PA1 f) the masking layer is removed, PA1 g) the surface on the anode side of the semiconductor body is covered with a contact layer. PA1 a) the anode side of the semiconductor body of the first conducting type is covered over its entire surface with a masking layer, PA1 b) the masking layer is structured by photolithography, PA1 c) in the semiconductor body, zones are generated according to its structure with higher doping than the anode base zone, PA1 d) the structured masking layer is removed, PA1 e) over the entire surface of the anode side of the semiconductor body, a doped layer of the second conducting type is generated, with a doping less than that of the zones of the first conducting type. PA1 f) the surface of the anode side of the semiconductor body is covered with a contact layer.
According to an alternative method, the purpose is accomplished by the following steps: